Flushing process for treating waste material

ABSTRACT

An Improved method of recovering and beneficially treating cellulosic fibers from compacted waste material containing waste paper before fibrillation by confining the waste material within a closed chamber containing a beneficially treating fluid and subjecting the contents of the closed chamber to one or more cycles of consecutive additions of beneficially treating fluid and removals of beneficially treating fluid.

BACKGROUND OF INVENTION

[0001] The present invention relates to an improvement of prior knownprocesses for processing compacted cellulosic fiber containing wastematerial (i.e. baled material or material in which the baling wires havebeen broken or loose material which has been compacted) for recovery ofhigh quality cellulosic fibers from waste material which usuallyconstitutes waste paper.

[0002] As discussed at some length in our prior U.S. Pat. Nos. 5,217,805and 5,496,439, before subjecting waste material containing cellulosicfibers to fibrillation stresses in a pulper, digester or slusher, it hasbeen practice to impregnate the cellulosic fiber-containing wastematerial with a debonding fiber softening and swelling liquid in aclosed pressure chamber under partial vacuum conditions which produces afiber-containing-liquid pulp of which the length and conditions of thecellulosic fibers are not seriously negatively affected by thefibrillation stresses of the pulpier.

[0003] The action of the partial vacuum condition has been to partiallyremove (or evacuate) the majority of the air from within compactedcellulosic fiber containing waste material and to replace the partiallyremoved air with a debonding and fiber softening and swelling liquid. Itwas learned that the deeper the partial vacuum the more the liquidimpregnated the cellulosic fiber-containing waste material and the moreextensive and effective the treatment. Contrary-wise it was also learnedthat the depth of the partial vacuum applied must be limited to avoiddeleterious evaporative drying of the cellulosic fibers. The action isdescribed as: Air Removal (or Evacuation)/Liquid Replacement.

BRIEF DESCRIPTION OF THE DRAWING

[0004]FIG. 1 comprises two graphs illustrating the quality of cellulosicfibers based on the Tear and Tensile strengths of the sheets they form.

[0005]FIG. 2 is a plot of the Tear Factor versus Breaking Length of thesheets formed of the fibers produced by our present invention and byprior inventions.

[0006]FIG. 3 is a schematic illustrating in part the process that isclaimed.

[0007]FIG. 4 is a plot of Air in Compacted Waste Paper.

[0008]FIG. 5 is a plot of Domains of Effectiveness of Prior “Remove &Replace” Inventions and of the New “Circulate, Flush & Refresh”Invention.

[0009] Table I. is a listing of the measurements for, of thecomputational steps and results of Air in Compacted Waste Paper.

SUMMARY OF INVENTION

[0010] The object of this invention is to recover high qualitycellulosic fibers from compacted cellulosic fiber-containing wastematerial. This is accomplished by confining the waste material in adebonding fluid-filled closed chamber and consecutively adding debondingfluid to the closed chamber and removing debonding fluid from the closedchamber. The debonding fluid that is removed from the closed chamber maybe partially spent. It has been observed that there is a partialcollateral loss of air from the compacted fiber-containing wastematerial and subsequently from the closed chamber during the processsteps in which debonding fluid is removed.

DETAILED DESCRIPTION OF THE INVENTION

[0011] Four pulp properties principally affect the strength quality ofpaper and paperboard produced from the pulp: fiber length, fiberstrength, fiber-to-fiber bond strength per unit of fiber-to-fibercontact area and fiber-to-fiber conformability. Tensile strength isdependent on fiber strength, fiber-to-fiber bond strength per unit offiber-to-fiber contact area and fiber-to-fiber conformability; thegreater each of these, the greater is the tensile strength. Out-of-planetear strength (Elmendorf Tear) is primarily dependent on fiber length;the longer the fiber length, the greater is the out-of-plane tearstrength. However tear strength can be adversely affected by the extentof bonding in paper/paperboard. The greater the tear strength at a givenlevel of tensile strength, the greater the fiber quality. The graphs ofFIG. 1 illustrate the quality comparisons of fiber based on Tear andTensile. The choice of the two graphs is dependent on the fiber species.

[0012] Because the standardized measurements of tear and tensile areaffected so differently by the four pulp properties, taken together theyare very effective in portraying pulp fiber quality. The greater thepulp quality, the less refining is required to comply with tensilestrength related specifications of paper and paperboard grades. The lessrefining required, the less pulp fiber fines are generated and drainageon the paper machine is less retarded. The greater the drainage, thegreater the potential for faster paper machine speed and higherproduction and the less the need for costly dry strength additives suchas starch.

[0013] Subsequent to the laboratory work reported in our U.S. Pat. No.5,496,439, which produces a cellulosic fiber-containing pulp bysubjecting the cellulosic fiber-containing compacted waste material toconsecutive negative and positive gage pressure conditions in thedebonding liquid-filled pressure chamber, further laboratory work hasbeen conducted comparing these prior art results to the pulp produced bysubjecting compacted cellulosic fiber-containing material to consecutiveadditions and removals of debonding liquid in a debonding liquid-filled,closed chamber.

[0014]FIG. 3 illustrates schematically the procedure in which air in thecompacted cellulosic fiber containing waste material acts in concertwith the addition and removal of the debonding liquid to flush thedebonding liquid in and out of the compacted material.

[0015] In FIG. 3 the air within the compacted material is shownschematically as initially and principally distributed throughout thecompacted waste material. After subsequent cycles of circulating,flushing and partial refreshing of debonding liquid in and out of thecompacted material the distribution of the air depends on its initiallocations in the compacted waste material.

[0016] A first part of the air is located in the interstices within thecellulosic fibers that are distributed throughout the compacted wastematerial. A second part of the air is located in the interstices betweenthe cellulosic fibers and remains largely distributed throughout thecompacted waste material with greater concentration towards the centerof the compacted waste material after cycles of adding debonding liquidto and removing debonding liquid from the closed chamber. A third partof the air is located in the interstices between the sheets and piecesof the compacted waste material; its distribution is largely skewedafter cycles of adding debonding liquid to and removing debonding liquidfrom the closed chamber with substantially more of the remaining thirdpart of the air near the center of the compacted material. Collaterallya substantial portion of the third part of the air is flushed out of thecompacted waste material by the cycles of adding debonding liquid to andremoving debonding liquid from the closed chamber. FIG. 3 illustratesthe collateral loss of some of the air. Collaterally less of the secondpart of the air is flushed out of the compacted waste material by thecycles of adding debonding liquid to and removing debonding liquid fromthe closed chamber. Collaterally still less of the first part of the airis flushed out of the compacted waste material by the cycles of addingdebonding liquid to and removing debonding liquid from the closedchamber. The scale of FIG. 3 does not allow illustration of the lessercollateral losses of the first and second parts of the air.

[0017] Our invention thereby circulates and flushes debonding liquid inand out of the compacted waste material structures by one or more cyclesof adding debonding liquid to and removing debonding liquid from theclosed chamber and relying on the trapped air in the compacted wastematerial to act as miniature expelling pumps to circulate, flush andpartially expel the debonding liquid containing partially consumeddebonding chemical(s) and replacing in part the partially spent treatingfluid with fresher debonding liquid. Paper and paper fiber tend to beacidic and neutralize the debonding fluid. By partially replacing thepartially neutralized debonding liquid with fresher debonding liquid,originally weaker debonding liquid can be utilized.

[0018] Other patented processes including our U.S. Pat. No. 5,217,805and U.S. Pat. No. 5,496,439 utilize the combination of partial vacuum toremove as much air from waste material containing waste paper and highpressure to force as much debonding liquid into the partially voidinterstices in the waste paper and cellulosic fibers as results inoptimal paper mill operations. Optimal operations are determined bytradeoff of effectiveness of swelling and debonding of the cellulosicfiber, and capital and operating costs and rate of production of processequipment. The depth of partial vacuum is limited by deterioration offiber properties by evaporative drying of cellulosic fiber.

[0019] Other processes remove air and replace with debonding liquid. Ournew invention utilizes air that is retained within the compacted wastematerial in combination with addition of debonding liquid to and removalof debonding liquid from a closed chamber containing waste materialcontaining waste paper to flush and circulate through and partiallyrefresh within the waste material containing waste paper containingcellulosic fibers.

[0020] In our improved process the compacted material is consecutivelyfilled with additional debonding liquid causing the air within thecompacted material to be compressed and occupy less space and thedebonding liquid to occupy the space vacated by the air. Upon removal ofdebonding liquid the first part of the air that was compressed withinindividual fibers expels the debonding liquid outwardly through thefiber and the second part of the air that was compressed between thefibers is flushed through and between adjacent fibers and the third partof the air flushes the debonding liquid through the paper and causescirculation, exchange and repositioning within the large intersticeswithin the compacted material and expels partially out of the compactedmaterial. Along with the partially spent debonding liquid from withinthe compacted material that is partially expelled there is collateralloss of air from within the compacted material. The air that is lost inprincipally the third part of the air along with less of the second partof the air and still less of the first part of the air. Successivecycles of addition of debonding liquid to and removal of partially spentdebonding liquid from the closed chamber and consequently to and fromthe compacted material adds fresher debonding liquid to and removespartially spent debonding liquid from the cellulosic fiber contained inthe compact material providing a fresher debonding liquid to swell anddebond the cellulosic fibers more effectively. An advantage is the useof a lower concentration of debonding liquid and associated reduction ofrequirements to neutralize the residual debonding liquid down stream inthe pulping and papermaking process.

[0021] In summary our new invention FLUSHES, CIRCULATES and REFRESHES;previously existing processes REMOVE(or EVACUATE) and REPLACE.

[0022] There are applications of greater effectiveness of these twodifferent processes. Remove and Replace are more effective debondingwaste paper containing cellulosic fibers that are most difficult fordebonding liquid to reach and contact. Milk Carton and Drink Boxes areexamples.

[0023] Flush, Circulate and Refresh are more effective debonding wastepaper containing cellulosic fibers that are less difficult for debondingliquid to reach and contact. OCC is a large market volume example.

[0024] An example of the use of our invention is its application to therepulping of Old Corrugated Containers (OCC). OCC is composed of linersor facings and fluted medium. The liners are normally chemically sizedto aid in stiffness retention under mildly wet conditions. Sizingadditives reduce the ability of fiber to swell under wet conditions.

[0025] Our invention addresses the affects of these anti-swellingadditives by flushing and circulating weak caustic solution in and outof the compacted OCC to partially expel the partially spent weak causticsolution containing the swelling additives and to partially exchange thepartially spent caustic solution with fresher caustic. Also, the causticthat is used to swell the fibers is partially exchanged with freshercaustic solution. Paper and paper fiber tend to be acidic and neutralizethe caustic. By partially exchanging the partially neutralized causticwith fresher caustic, weaker caustic solutions can be utilized.Accordingly, one of the aspects of the improved process of our inventionis removing anti-swelling chemical additives from sized paper andpaperboard, and partially exchanging the partially neutralized causticwith fresher caustic.

[0026] Some results of our further laboratory work utilizing OCC arerepresented by the FIG. 2 graph of Tear Factor versus Breaking Length(i.e. Tensile) of the sheets made from the resulting fiber. The eightgraphs in FIG. 2. plot the TEAR FACTOR versus BREAKING LENGTH results ofeight Valley Beater test runs conducted on samples of OCC. Note thatBREAKING LENGTH is a tensile property that describes TENSILE STRENGTH.Therefore the eight graphs are Tear-Tensile diagrams. Of these eightsamples of OCC in FIG. 2, seven samples designated 250 mm, 450 mm, PO450mm, 600 mm, 760 mm, 761oldcor and 1000oldcor were compacted and treatedby the process of our new invention as shown in the schematic labeledFIG. 3 as follows:

[0027] Before fibrillation in a Valley Beater each of the samples ofcompacted OCC 2 was placed in a laboratory size closed chamber 1 and thechamber was filled with a weak caustic solution 3. Subsequently eachsample was subjected to two cycles of consecutive additions 4 andremovals 5 of weak caustic solution. The air in the compacted OCC actedin concert with the addition and removal of the weak caustic solution tocirculate, flush and refresh weak caustic in and out of and within thecompacted OCC. The process relied on the trapped air in the OCC to actas miniature pumps to circulate, flush and partially exchange thepartially consumed weak caustic solution in the compacted OCC samples.

[0028] The eighth sample designated 25 mm in FIG. 2 was processed inaccordance with our prior U.S. Pat. No. 5,496,439 in which the processparameters were set such that very little air was trapped in thecompacted OCC in the weak caustic solution in the closed chamber.

[0029] It is evident from FIG. 2. that the strength results of all eighttests are substantially the same within experimental error. There weretwo very important differences. First, it was observed that the weakcaustic solution surrounding the compacted OCC turned dark during thecirculating, flushing and refreshing of the weak caustic solution in thecompacted OCC in the processing of the seven samples processed inaccordance with our new invention whereas there was very littledarkening of the weak caustic solution during the processing of theeighth sample in which weak caustic solution replaced the air which hadbeen removed in accordance with our prior U.S. Pat. No. 5,496,439utilizing a first vacuum of only 25 mmHg absolute. Second, lower costequipment requiring shorter processing time and consuming less energyare required to conduct the process steps of our new invention.

[0030] Table I. and the FIG. 4 graph of Air in Compacted OCC illustratesome results of our still further laboratory work utilizing OCC. Theexperiments were conducted to measure the pounds of air per ton of OCCfirst trapped in compacted OCC in the closed chamber during itsprocessing. Table I. lists the data and tabulates the steps in thecalculation of pounds of air per ton of OCC. FIG. 4 illustrates astraight line regression on semi-logarithm coordinates. It has beenobserved in these five experiments and in other laboratory experimentsconducted after the preparation of our U.S. Pat. No. 5,496,439 that atconditions of weak caustic solution addition to and air removal from theclosed chamber containing samples of OCC which resulted in greater than0.09 pounds of air per ton of OCC trapped in the compacted OCC the weakcaustic solution surrounding the compacted OCC turned dark duringsubsequent additions and removals of weak caustic solution whereas atconditions of weak caustic solution addition to and air removal from theclosed chamber containing samples of OCC which resulted in less than0.09 pounds of air per ton of OCC trapped in the compacted OCC the colorof the weak caustic solution surrounding the compacted OCC remainrelatively unchanged. There was a range of transition in color above andbelow 0.09 pounds of air per ton of OCC. There was also a shifting ofthe transition value of 0.09 pounds of air per ton of OCC depending onthe particular source and composition of the OCC of the various otherthe experiments.

[0031] Thus we have discovered that there are important improvements inthe treatment of compacted OCC which can be a obtained by the process ofour new invention which primarily circulates, flushes and partiallyexchanges the weak caustic solution in the compacted OCC compared to theprocess of our earlier inventions which primarily partially remove airfrom within and the compacted OCC and partially replace it with weakcaustic solution. We have also discovered how to determine the amount oftrapped air that is necessary to practice our new invention.

[0032] A loose analogy of our new invention could be drawn to thebehavior of a kitchen sponge. It is only a loose analogy because asponge's ability to pump liquids out of its mass resides in the elasticexpansivity of its compressed solid matrix whereas the ability or ourprocess to pump liquids out resides in the expansivity of the airtrapped in the compacted waste material.

[0033]FIG. 5 titled Domains of Effectiveness of Our Prior “Remove &Replace” Inventions 7 and Our New “Circulate, Flush & Refresh” Invention10 illustrates schematically these domains. In our previous inventionspartial evacuation of air in the compacted material is limited by thedeleterious affect of excessive evaporative drying of the fibers. Themoisture conduct of good quality cellulosic fibers is about 6% to 7%.Reducing this moisture content enbrittles cellulosic fibers irreversiblyweakening them and reducing their conformability and bondablity. Thislower limit is illustrated in FIG. 5 by a light vertical line 6. Lesserpartial evacuation results in less replacement by a debonding liquidthat results in turn in less effective treatment 8of the compacted wastematerial by treatment liquid replacement.

[0034] However un-replaced trapped air begins to contribute to thetreatment benefits of circulating, flushing and refreshing the debondingliquid. A transition value of VA or PA is reached 9 beyond whichcirculating, flushing debonding liquid 10 are more effective thanremoving air from the compacted waste material and replacing it withdebonding liquid 7. This is the beginning of the domain in which our newinvention 10 is more effective than our previous inventions 7. Thegreater the amounts of debonding liquid added to and debonding liquidremoved from the closed chamber, the more effective is the treatmentprovided by the process of our new invention. As greater amounts ofdebonding liquid are added to the compacted material with increasedamounts of trapped air the energy to add the debonding liquid and thestructural elements of the closed chamber, the access door(s), thevalves, the accumulation pressure chambers and the high pressure pumpsbecome increasingly expensive and cycle time can become longer. Therebythe cost-effectiveness diminishes 11 as illustrated in FIG. 5. Theoverlap of the two domains of effectiveness is illustrated in FIG. 2.where the quality of the fiber from the treatment is the same withinexperimental error.

[0035] There are two methods of controlling the schedules of adding adebonding liquid to the closed chamber. The first method utilizesprocess measurement instruments to calculate the mathematical value ofthe quantity {ΔV₁₂/[W(1/p₁−1/p₂)]} in which, during the first cycle ofadding debonding liquid, p₁ is a first absolute pressure in pounds persquare foot in the closed chamber at a first time and p₂ is a secondabsolute pressure in pounds per square foot in the closed chamber at asecond time and ΔV₁₂ is the volume in cubic feet of debonding liquidadded between the first time and the second time and W is the dry weightin pounds of the compacted waste material and equipment to control theaddition of a debonding liquid into the closed chamber at a firstschedule of flow rate and removing air from the closed chamber at asecond schedule of flow rate such that the mathematical quantity is atleast the value VA. The value VA is determined in the laboratory asdescribed above. The value VA we measured and concluded from laboratoryobservations is 1.27 feet for the OCC that we evaluated.

[0036] The second method which is more approximate is to control theaddition of a debonding liquid into the closed chamber at a firstschedule of flow rate and removal air from the closed chamber at asecond schedule of flow rate such that the average pressure at themidpoint in the closed chamber is PA. The value PA is 160 mmHg absolutefor the OCC that we evaluated.

[0037] It is apparent to those skilled in the art that other TreatmentFluids, which provide other recovered fiber improvements, can beutilized in the process of our invention. Other recovered fiberimprovements can include fiber bleaching, fiber coloration, fiberdeinking, fiber deodorizing and fiber-plastic debonding. Although lesseffective, it is also apparent to those skilled in the art that other,non-miscible fluids can be utilized in the consecutive cycles of addingto and removing from the closed chamber. This less effective use ofnon-miscible fluids would require that the closed chamber be constructedsuch that the Treatment Fluid not uncover the compacted material untilthe treatment process is completed. TABLE I Air in Compacted OCCEquations for sample 1 Air weight calculations utilizing 400 gram sampleof OCC data point C in column C 2 3 Cross-sectional Area Of LaboratoryClosed Pressure Chamber - square mm 4744 C17 $C3*C15 4 Hg. Density 13.6C18 C17 5 Cubic mm/cubic feet 28316847 C19 C17*(C13 + C16/$C4)/(C14-C13-C15/$C4) 6 Grams/pound 453.6 C20 C18 + C19 7 Pounds/ton 2000 C21 (C14 +((C16- C15)/$C4))/($C9*$C8) 8 Air std. atm. spec vol. - cubic feet/pound13.08 C22 (C13 + C16/$C4)/($C9 *$C8) 9 Air std. atm. pressure - mm Hg.760 C25 ((C22*C20/$C5)/(400/$C6))*$C7 10 11 Datapoints C D E F G 12 13p1 = Fill pressure - mm HG abs 250 25 760.4 450 450 14 p2 = pressureafter addtion of air to top of closed pressure chamber - mm Hg abs 5936767.4 5936 5936 772 15 Drop in free surface of weak caustic soluionafter air additionHeight difference - mm 15 30 31 14 6 16 Distance fromfree surface @ p1 to center of compacted OCC - mm 215 215 215 215 215 17Weak caustic solution volume forced into compacted OCC by air addtion -cubic mm 71160 142320 147064 66416 28464 18 V1-V2 = Decrease in volumeof air in compacted OCC saused by 71160 142320 147064 66416 28464 airaddtion - cubic mm 19 V2 = Compacted volume @ p2 + (compacted distancedown to V2)/13.6 - cubic mm 3327 7846 22066 5640 41233 20 V1 = Initialvolume @ p1 + (initial distance down to V1)/13.6 - cubic mm 74487 150166169130 72056 69697 21 Compacted density in V2 -lbs/cubic foot 0.598610.07857 0.59850 0.59862 0.07921 22 Initial density in V1 - lbs/cubicfoot 0.02674 0.00411 0.07808 0.04686 0.04686 23 24 Fill pressure-mm HG250 25 760.4 450 450 25 Air in Compacted OCC - lbs. air per ton OCC0.15952 0.04937 1.05773 0.27043 0.26158

What is claimed is:
 1. A process for recovering and beneficiallytreating cellulosic fiber from compacted waste material containing wastepaper in which before fibrillation of the waste paper the waste materialis confined in a closed chamber containing a beneficially treating fluidcomprising one or more cycles of the consecutive steps of: a) addingadditional beneficially treating fluid to said closed chamber and b)removing beneficially treating fluid from said pressure chamber.
 2. Aprocess for recovering cellulosic fiber from compacted waste materialcontaining waste paper in which before fibrillation of the waste paperthe waste material is confined in a closed chamber containing adebonding liquid comprising one or more cycles of the consecutive stepsof: a) adding additional debonding liquid to said closed chamber and b)removing debonding liquid from said pressure chamber.
 3. A process forrecovering and beneficially treating cellulosic fiber from compactedwaste material containing waste paper in which before fibrillation ofthe waste paper the waste material is confined in a closed chambercontaining a beneficially treating liquid comprising a first step of:(a) adding a beneficially treating liquid into said closed chamber at afirst schedule of flow rate and removing air from said closed chamber ata second schedule of flow rate such that the mathematical value of thequantity {ΔV₁₂/[W(1/p₁−1/p₂)]} is at least the value VA in feet duringthe first cycle of step (b) below in which p₁ is a first absolutepressure in pounds per square foot in said closed chamber at a firsttime and p₂ is a second absolute pressure in pounds per square foot insaid closed chamber at a second time and ΔV₁₂ is the volume in cubicfeet of beneficially treating liquid added between said first time andsaid second time and W is the dry weight in pounds of said compactedwaste material and where the value of VA in feet is measured in thelaboratory and concluded from observations in the laboratory for thegrade of waste material being processed and one or more cycles of theconsecutive steps of: (b) adding additional beneficially treating liquidto said closed chamber and (c) removing beneficially treating liquidfrom said pressure chamber.
 4. A process for recovering and beneficiallytreating cellulosic fiber from compacted waste material containing wastepaper in which before fibrillation of the waste paper the waste materialis confined in a closed chamber containing a beneficially treatingliquid comprising a first step of: (a) adding a beneficially treatingliquid into said closed chamber at a first schedule of flow rate andremoving air from said closed chamber at a second schedule of flow ratesuch that the average pressure at the midpoint in the closed chamber isat least the value PA and where the value of PA is measured in thelaboratory and concluded from observations in the laboratory for thegrade of waste material being processed and one or more cycles of theconsecutive steps of: (b) adding additional beneficially treating liquidto said closed chamber and (c) removing beneficially treating liquidfrom said pressure chamber.
 5. A process for recovering cellulosic fiberfrom compacted waste material containing waste paper in which beforefibrillation of the waste paper the waste material is confined in aclosed chamber containing a debonding liquid comprising a first step of:(a) adding a debonding liquid into said closed chamber at a firstschedule of flow rate and removing air from said closed chamber at asecond schedule of flow rate such that the mathematical value of thequantity {ΔV₁₂/[W(1/p₁−1/p₂)]} is at least the value of VA in feetduring the first cycle of step (b) below in which p₁ is a first absolutepressure in pounds per square foot in said closed chamber at a firsttime and p₂ is a second absolute pressure in pounds per square foot insaid closed chamber at a second time and ΔV₁₂ is the volume in cubicfeet of beneficially treating liquid added between said first time andsaid second time and W is the dry weight in pounds of said compactedwaste material and where the value of VA in feet is measured in thelaboratory and concluded from observations in the laboratory for thegrade of waste material being processed and one or more cycles of theconsecutive steps of: (b) adding additional debonding liquid to saidclosed chamber and (c) removing debonding liquid from said pressurechamber.
 6. A process for recovering cellulosic fiber from compactedwaste material containing waste paper in which before fibrillation ofthe waste paper the waste material is confined in a closed chambercontaining a debonding liquid comprising a first step of: (a) adding adebonding liquid into said closed chamber at a first schedule of flowrate and removing air from said closed chamber at a second schedule offlow rate such that the average pressure at the midpoint in the closedchamber is at least the value PA and where the value of PA is measuredin the laboratory and concluded from observations in the laboratory forthe grade of waste material being processed and one or more cycles ofthe consecutive steps of: (b) adding additional debonding liquid to saidclosed chamber and (c) removing debonding liquid from said pressurechamber.
 7. A process for recovering cellulosic fiber from compacted OCCin which before fibrillation of the OCC the OCC is confined containing aweak caustic solution in a closed chamber comprising a first step of:(a) adding weak caustic solution into said closed chamber at a firstschedule of flow rate and removing air from said closed chamber at asecond schedule of flow rate such that the mathematical value of thequantity {ΔV/[W(1/p₁−1/p₂)]} is at least 1.27 feet during the firstcycle of step (b) below in which p₁ is a first absolute pressure inpounds per square foot in said closed chamber at a first time and p₂ isa second absolute pressure in pounds per square foot in said closedchamber at a second time and ΔV is the volume in cubic feet of debondingliquid added between said first time and said second time and W is thedry weight in pounds of said compacted OCC and one or more cycles of theconsecutive steps of: (b) adding additional weak caustic solution tosaid closed chamber and (c) removing weak caustic solution from saidpressure chamber.
 8. A process for recovering cellulosic fiber fromcompacted OCC in which before fibrillation of the OCC the compacted OCCis in a closed chamber confined containing a weak caustic solutioncomprising a first step of: (a) adding weak caustic solution into saidclosed chamber at a first schedule of flow rate and removing air fromsaid closed chamber at a second schedule of flow rate such that theaverage pressure at the midpoint in the closed chamber is at least 160mmHg absolute and one or more cycles of the consecutive steps of: (b)adding additional weak caustic solution to said closed chamber and (c)removing weak caustic solution from said pressure chamber.
 9. A processfor recovering cellulosic fibers from compacted waste materialcontaining waste paper in which before fibrillation the waste materialis confined in a closed pressure chamber containing a fiber debondingliquid comprising one or more cycles of the consecutive steps of: (a)connecting said pressure chamber to a debonding liquid supply having apressure above 760 mm absolute and (b) reducing the pressure within saidpressure chamber to no more 760 mm absolute.
 10. The process of claim 9wherein step (b) comprises reducing the pressure within said pressurechamber to within 250-600 mm absolute.